1. Field of the Invention
The present invention relates to a heat dissipating fan with an airflow guiding structure.
2. Description of Related Art
A typical conventional heat dissipating fan is disclosed in, e.g., U.S. Pat. Nos. 5,522,700, 5,584,339 and 5,582,506 and includes a cover plate, an impeller, and a heat dissipating plate. The cover plate includes an air inlet and a base, and the impeller is mounted to an upper side or an underside of the cover pate. The heat dissipating plate is mounted to an object to be dissipated, such as a central processing unit. In operation, the impeller forces the air from the inlet to move toward the heat dissipating plate for dissipating heat.
The airflow can, however, only move outward along the extending direction of the fins on the heat dissipating plate, and the heat dissipation effect can only be achieved through the heat dissipating plate. The heat dissipating fan could neither guide and expel the airflow directly downward nor directly provide a heat dissipating effect for an object located right below the heat dissipating fan. Further, a fan unit consisting of a cover plate and an impeller must be used with a heat dissipating plate. Application of the fan unit consisting of a cover plate and an impeller is limited, and it is difficult to reduce the cost for manufacturing various types of heat dissipating fans. Further, the air inlet amount could not be effectively increased, as the impeller can only drive air in via the air inlet of the cover plate. Further, the wind pressure could not be increased. As a result, the application of the heat dissipating fan is limited, and the heat dissipating efficiency is poor.
Another typical conventional heat dissipating fan disclosed in, e.g., Taiwan Utility Model Publication No. 540641, is an axial fan including a casing and an impeller. The impeller is rotatably mounted on a base provided on an air outlet side of the casing. On an air inlet side of the casing, a plurality of radial inlets extend from an air inlet toward a periphery of the casing. An air gain guiding plate extends radially outward from the respective blade on the impeller and aligns with the respective radial inlet, thereby increasing the air inlet amount.
However, the impeller must be mounted on the base of the casing such that the casing of a certain specification can only be used with an impeller of a corresponding specification, resulting in a limited application of the casing and the impeller and thus failing to effectively reduce the cost for manufacturing various types of heat dissipating fans.
Further, since the respective air gain guiding plates can only drive the air to pass through the respective radial inlets and since the air is driven inward and downward by the respective air gain guiding plates, turbulence is generated in a joint area between the periphery of the respective radial inlet and an inner periphery of the casing. As a result, provision of the air gain guiding plates results in wind noise. Further, the axial flow fan could not increase the wind pressure. Application of the axial flow fan is limited and the heat dissipating fan is unsatisfactory.